The present invention relates to a method for controlling a refilling motor of a power train of a hybrid vehicle, which includes a pressure accumulator which supplies a hydraulic power machine. It also relates to a power train and an automobile that implements this control method.
Certain types of hybrid vehicles have a power train which includes an internal combustion engine delivering mechanical energy which drives a hydraulic pump in order to refill hydraulic pressure accumulators for storing this energy.
These vehicles moreover have a hydraulic machine connected to driving wheels, which can function either as a motor in order to deliver mechanical power to the driving wheels by taking stored energy from the pressure accumulators, or as a pump in order to fill these accumulators by braking the vehicle in such a way as to recover the kinetic energy of the vehicle. The stored energy is subsequently restored to the hydraulic machine functioning as motor, for powering the vehicle.
The hydraulic machine generally has a variable displacement, in order to adjust the levels of torque and power that are delivered or absorbed.
This use of stored hydraulic energy makes it possible to optimize the functioning of the internal combustion engine and to reduce its fuel consumption as well as its emission of polluting gases. The storage of hydraulic energy moreover enables one to run in hydraulic mode with zero emission, “ZEV”, with the internal combustion engine remaining at a stop.
As a variant, the hybrid vehicle can have an electric motor that drives the pump for refilling the pressure accumulators, in order to store hydraulic energy coming from an electrical energy source in these accumulators.
A known method, presented in particular by the document WO-A1-9854450, describes a management of the power train in order to maintain approximately constant pressures in the hydraulic accumulators.
However, in order to optimize the functioning of the power train, one generally seeks to make the best possible use of the pressure accumulators by using a large quantity of energy in each cycle, by raising the pressure to the maximum threshold and then emptying them to a minimum threshold in order to delay the start-ups of the refilling motor and to space out these start-ups.
A problem arising then is the optimization of the instant of restarting of the motor, taking into account the time necessary for its start-up, and without risking a lack of pressure in the hydraulic accumulator which would lead to a loss of power on the driving wheels of the vehicle